Add to_csv/read_csv support for RegularTimeSeries and IrregularTimeSe… #80

Job	Run time
testing HECDSS functions (ubuntu-latest)	22s
testing HECDSS functions (windows-latest)	42s
Build Distribution	21s
Publish Development Distribution	14s
Publish Release Distribution	14s
Create Signed GitHub Release	0s
	1m 53s

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